Global Analysis of lithosphere-asthenosphere dynamics using a revised plate cooling model

A global understanding of the evolution of oceanic lithosphere yields key insights about lithosphere-asthenosphere interaction. An important starting point is that age-depth and heatflow measurements provide the fundamental constraints for progressive cooling of oceanic lithosphere. When jointly inverting these measurements to identify an optimal plate model, the robustness of the result is predicated upon their quality, number and global distribution. Here, we exploit a revised and extensively augmented database of accurate age-depth measurements (n = 10,874) and a published database of heatflow measurements (n = 3,753). These databases are jointly modelled using both analytical and numerical methodologies to obtain a plate model, which has an average asthenospheric temperature of 1325±50oC and a lithospheric thickness of 105±10 km. These recovered values agree with independent geochemical and seismic constraints of mantle potential temperature and lithospheric thickness. This revised plate cooling model is used to improve our understanding of lithosphere-asthenosphere interaction.  First, we use plate cooling to measure residual depth anomalies, which are a reliable proxy for mantle dynamic topography. Our results demonstrate that dynamic topography varies on wavelengths as short as 1000 km with amplitudes of ±1 km. Secondly, we combine plate cooling with the depth distribution of oceanic intraplate earthquakes to identify the isothermal surface above which brittle elastic behaviour occurs. Finally, we demonstrate that age-depth and heatflow measurements exhibit a sustained flattening from ~60 Ma, suggesting that resupply of heat from the asthenosphere is an essential component of the lithosphere-asthenosphere system. Our database of accurate residual depth measurements is used to explore links between mantle dynamics, asthenospheric temperature anomalies extracted from earthquake tomographic models, and basaltic melting.